1. Field of the Disclosure
The present disclosure relates to a bullet-resistant laminated glass having at least three sheets of glass in which one of the sheets of glass faces the impact side as a cover sheet, and one glass sheet is formed as a closure sheet facing away from the impact side.
2. Description of the Related Art
Bullet-resistant glass in the form of laminated glass has been known for several decades. It is usually composed of a plurality of glass sheets that are connected to one another with intermediate film layers. These laminated glasses are designed in numerous variations. For example, they are equipped with laminated plastic intermediate layers or with coatings or films that face away from the impact and bind glass splinters. They are also sealed, in part, with a plastic sheet facing away from the impact. Test standards, including the European Standard EN 1063, distinguish between sheets “with splinter output” and sheets “without splinter output” within the individual impact classes. These different classifications require the use of laminated glasses of different thicknesses or different glass designs.
In order to be able to fulfill the requirement of the standard for laminated glass free of splinter output in the architectural field, thick laminated glass must be provided. In particular, clearly greater glass thicknesses are necessary than in a laminated glass which simply protects against bullets. For soft-core bullets, the difference in thickness for sheets “with splinter output” and “without splinter output” amounts to up to 50% within the respective projectile or impact class. Due to the increase in thickness and in weight caused by this, the applicability of laminated glasses is made difficult or is hindered. In particular, special constructions are necessary in part for door, window and frame systems. Due to the greater weight, special fastenings are necessary, for example, hinge structures.
In order to counteract such an undesired increase in weight for laminated glasses “without splinter output”, frequently a plastic sheet made of polycarbonate, polymethyl methacrylate or the like, which faces away from the impact, is laminated or glued on. Such a solution is disclosed in EP 0 157 646 or DE 10 2008 043 718.
In addition, laminated glasses are known in which a splinter-binding coating facing away from the impact is introduced onto the laminated glass. Such a design variant is disclosed in DE 692 27 344. Both the plastic sheet that is introduced and the splinter-binding coatings are mechanically sensitive. In particular, they are not scratch-resistant. They cannot be properly cleaned, and can be cleaned only with special cleaning agents. In addition, they are at risk of aging, for example, due to UV irradiation. This is a serious disadvantage for use in the field of architecture.
In order to increase ballistic performance, laminated glasses in which chemically or thermally pre-stressed glasses facing the impact side are used are known from the prior art. These glasses then form a cover layer, which breaks up the penetrating bullet or deforms it. The bullet, in fact, then disrupts the cover sheet. However, the splinter output on the back side cannot be prevented by this measure. Therefore, frequently polycarbonate sheets or the like facing away from the impact are used in these glasses also.